Re: Q:efficient list operation wanted

• To: mathgroup at smc.vnet.net
• Subject: [mg13994] Re: Q:efficient list operation wanted
• From: Allan Hayes <hay at haystack.demon.co.uk>
• Date: Sat, 12 Sep 1998 16:59:17 -0400
• Sender: owner-wri-mathgroup at wolfram.com

```Klaus Duellmann wrote:
>
> I am looking for an efficient solution of the following problem:
>
> Given two lists L1 = {1,2,3,4,5,3,7,2,3,9} and L2 = {a, b, c}
>
> I want to replace all numbers 3 in L1 by the elements of L2
> successively,
> that is the first 3 by a, the second 3 by b and the third 3 by c. That
> is I want to get the following modified L1-list: {1,2,a,4,5,b,7,2,c,9}.
>
> Replace[] unfortunately replaces elements with a single element only. Is
> there a chance to avoid hideous Do-Loops?
>
> Any hints are appreciated!
>
> PS. Remove XXX from my e-mail-address
>
> K. Duellmann

Klaus:

L1 = {1,2,3,4,5,3,7,2,3,9} ;
L2 = {a, b, c};

L1[[Flatten[Position[L1,3]]]]= L2;

L1

{1,2,a,4,5,b,7,2,c,9}

Allan

--
Allan Hayes
Training and Consulting
Leicester, UK
hay at haystack.demon.co.uk
http://www.haystack.demon.co.uk
voice: +44 (0)116 271 4198
fax: +44 (0)116 271 8642

```

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